1. Field of the Invention
The field of art to which this invention relates is-printers, in particular, a feed enhancer for a high volume printer having a top-feeder in which paper stock having labels and/or perforations are fed into the printer.
2. Description of the Related Art
In printers of the prior art, particularly those which employ a top-feeder for storing and feeding paper into the printer, paper which has a label affixed thereto or which has one or more perforations presents a problem in that it does not properly feed into the printer. Printing on such paper is particularly troublesome because the paper does not sit flatly upon a feeder tray due to the labels or perforations.
A typical printer 100 of the prior art having such a top-feeder paper feed arrangement is shown in FIGS. 1A and 1B. The top-feeder 102 generally includes a paper tray 103 and employs a pick roller 104 for contacting and feeding a sheet of paper 106 from the top of a paper stack 108 into the printer 100. A gearbox and motor assembly 110 drive the pinch roller as necessary to feed the paper 108. If the paper in the paper stack 108 does not sit flatly on the paper tray 103, the pick roller 104, which is generally located in the center of the paper along a central axis C--C, does not effectively engage and feed the paper 108 into the printer 100.
Examples of types of paper which do not lie flatly on the paper tray 103, are illustrated in FIGS. 2A-2C. Respective stacks of the types of paper illustrated in FIGS. 2A-2C are illustrated in FIGS. 3A-3C together with the paper tray 103 and pick roller 104 of FIG. 1.
FIG. 2A illustrates a sheet of paper 200 having a label 202 on one side. The label 202 adds a significant thickness to the overall thickness of the sheet of paper 200 in the area of the label 202. As can be seen in FIG. 3A, when stacked on a paper tray 103 of a printer 100 having a top feeder 102, the paper 200 has a greater height (H1) on the side with the label 202 than the height (H2) on the side without the label 202. Because of this uneven height (H1&gt;H2), the pick roller 104 only engages the paper 200 on a portion of its width and causes the paper 200 to rotate as it is being fed into the printer 100.
FIG. 2B illustrates a sheet of paper 210, having two perforations 212. The perforations 212 run in the same direction as the direction that the paper 210 is fed into the printer 100. As can be seen in FIG. 3B, when stacked on a paper tray 103 of a printer 100 having a top feeder 102, the paper 210 has a greater height (H3) on the sides than in the middle (H4) (alternatively, if the paper stack is turned 180 degrees such that the top sheet is at the bottom, the paper stack will have a peak at each of the perforations resulting in an M-shaped stack). Because of this uneven height (H3&gt;H4), the pick roller 104 does not properly engage the paper 210 leading to improper feeding of the paper 210 into the printer 100.
FIG. 2C illustrates a sheet of paper 220, having a single perforation 222. The perforation 222 runs in a direction perpendicular to the direction that the paper 220 is fed into the printer 100. As can be seen in FIG. 3C, when stacked on a paper tray 103 of a printer 100 having a top feeder 102, looking from the side of the paper stack, a portion 224 of the paper 220 decreases in height from the perforation 222 to the end of the paper 226. (alternatively, if the paper stack is turned 180 degrees such that the top sheet is at the bottom, the portion 224 will increase in height from the perforation 222 to the end of the paper 226). Because of this uneven height, the pick roller 104 does not properly engage the paper 210 leading to improper feeding of the paper 210 into the printer 100.
These problems ultimately cause the paper 200, 210, 220 to jam in the printer 100 resulting in downtime of the printer 100 and possibly, expensive maintenance. It should be apparent to those skilled in the art, that these paper configurations are given by way of example only and not as an exhaustive listing thereof. For example the paper may have a combination of those shown or others not shown such as pre-printed stock which has a tendency to curl when stacked upon the printer tray 103.
Devices are known in the prior art for addressing the uneven thickness and shape of paper to be fed into a printer. The prior art teaches devices for compensating for variations in the thickness between individual sheets of a paper stack being fed into a printer. The prior art devices achieve their objective by sensing the thickness of each piece of paper being fed into the printer and adjusting certain parameters within the printer according to the sensed thickness.
While these devices have their advantages, they are generally complex, costly, and difficult to implement on existing printer designs.
For these reasons a feed enhancer is needed which is simple, inexpensive, easy to retrofit onto existing printers and which can compensate for paper stacks that do not lie flatly and evenly upon a printer feeder which are to be fed into a printer, particularly one which employs a top-feeder system.